356 research outputs found
How large should whales be?
The evolution and distribution of species body sizes for terrestrial mammals
is well-explained by a macroevolutionary tradeoff between short-term selective
advantages and long-term extinction risks from increased species body size,
unfolding above the 2g minimum size induced by thermoregulation in air. Here,
we consider whether this same tradeoff, formalized as a constrained
convection-reaction-diffusion system, can also explain the sizes of fully
aquatic mammals, which have not previously been considered. By replacing the
terrestrial minimum with a pelagic one, at roughly 7000g, the terrestrial
mammal tradeoff model accurately predicts, with no tunable parameters, the
observed body masses of all extant cetacean species, including the 175,000,000g
Blue Whale. This strong agreement between theory and data suggests that a
universal macroevolutionary tradeoff governs body size evolution for all
mammals, regardless of their habitat. The dramatic sizes of cetaceans can thus
be attributed mainly to the increased convective heat loss is water, which
shifts the species size distribution upward and pushes its right tail into
ranges inaccessible to terrestrial mammals. Under this macroevolutionary
tradeoff, the largest expected species occurs where the rate at which
smaller-bodied species move up into large-bodied niches approximately equals
the rate at which extinction removes them.Comment: 7 pages, 3 figures, 2 data table
Isokinetic muscle function comparison of lower limbs among elderly fallers and non-fallers
O objetivo deste estudo foi identificar se hĂĄ diferenças entre o desempenho muscular de tornozelo, joelho e quadril em idosos com e sem relato de queda nos Ășltimos seis meses. Foram incluĂdos 81 idosos com 65 anos ou mais: 56 negaram quedas (G1) e 25 relataram quedas (G2). Utilizou-se o questionĂĄrio perfil de atividade humana para medir o nĂvel de atividade fĂsica, e o dinamĂŽmetro isocinĂ©tico para mensurar os parĂąmetros fĂsicos da função muscular. Os grupos nĂŁo diferiram entre si em relação Ă idade (p=0,925), duração (p=0,065) e frequĂȘncia (p=0,302) da prĂĄtica do exercĂcio fĂsico, Ăndice de massa corpĂłrea (p=0,995) e nĂvel de atividade fĂsica (p=0,561). O G2 apresentou menor desempenho para as variĂĄveis pico de torque de flexĂŁo e extensĂŁo de joelho esquerdo (p=0,027 e p=0,030, respectivamente) e trabalho por peso corporal (p=0,040) de flexĂŁo de joelho esquerdo a 60°/s; pico de torque e trabalho por peso corporal de flexĂŁo e extensĂŁo de joelho a 180°/s bilateralmente (p<0,050); e potĂȘncia mĂ©dia de flexĂŁo de joelhos direito e esquerdo (p=0,030). A maioria das variĂĄveis do tornozelo e quadril nĂŁo apresentou diferenças entre os grupos. Apenas a variĂĄvel pico de torque de extensĂŁo de quadril esquerdo foi significativamente maior no G1 (p=0,035). Ă importante considerar a função muscular do joelho na avaliação clĂnica de idosos para direcionar a intervenção terapĂȘutica e a prevenção de quedas.The aim of this study was to identify whether there are differences between the performance of muscular groups of ankle, knee and hip among elderly people who didn't have falls and individuals who reported falls in the last six months. The study included 81 elderly aged 65 or older: 56 non-faller subjects (G1) and 25 faaller subjects (G2). To obtain the level of physical activity, the questionnaire Human Activity Profile was used, and the muscle function of the lower limbs was assessed using isokinetic dynamometer. The groups did not differ regarding age (p=0.925), duration (p=0.065) and frequency (p=0.302) of the practice of physical exercise, body mass index (BMI) (p=0.995) and level of physical activity (p=0.561). The G2 showed a lower performance of peak torque of left knee flexion and extension (p=0.027 and p=0.030, respectively) and work proportional to body weight (p=0.040) of left knee flexion at 60°/s; peak torque and work proportional to body weight of bilaterally knee flexion and extension at 180°/s (p<0.05) and average power of right and left knee extension (p=0.03). Most variables of ankle and hip joints did not differ between groups. Only peak torque of left hip extension was significantly higher in the non-faller group (p=0.035). It is important to consider knee muscle function in the clinical evaluation of elderly in order to make the intervention more assertive and thus to prevent falls
Evidence for distinct coastal and offshore communities of bottlenose dolphins in the north east Atlantic.
Bottlenose dolphin stock structure in the northeast Atlantic remains poorly understood. However, fine scale photo-id data have shown that populations can comprise multiple overlapping social communities. These social communities form structural elements of bottlenose dolphin (Tursiops truncatus) [corrected] populations, reflecting specific ecological and behavioural adaptations to local habitats. We investigated the social structure of bottlenose dolphins in the waters of northwest Ireland and present evidence for distinct inshore and offshore social communities. Individuals of the inshore community had a coastal distribution restricted to waters within 3 km from shore. These animals exhibited a cohesive, fission-fusion social organisation, with repeated resightings within the research area, within a larger coastal home range. The offshore community comprised one or more distinct groups, found significantly further offshore (>4 km) than the inshore animals. In addition, dorsal fin scarring patterns differed significantly between inshore and offshore communities with individuals of the offshore community having more distinctly marked dorsal fins. Specifically, almost half of the individuals in the offshore community (48%) had characteristic stereotyped damage to the tip of the dorsal fin, rarely recorded in the inshore community (7%). We propose that this characteristic is likely due to interactions with pelagic fisheries. Social segregation and scarring differences found here indicate that the distinct communities are likely to be spatially and behaviourally segregated. Together with recent genetic evidence of distinct offshore and coastal population structures, this provides evidence for bottlenose dolphin inshore/offshore community differentiation in the northeast Atlantic. We recommend that social communities should be considered as fundamental units for the management and conservation of bottlenose dolphins and their habitat specialisations
Changes in stable isotope compositions during fasting in phocid seals
This study was supported by NSF grant #0213095 and by FRFC grant #2.4502.07 (F.R.S.-FNRS).Rationale: The grey seal, Halichoerus grypus (GS), and the northern elephant seal, Mirounga angustirostris (NES), come ashore for reproduction. This period involves intense physiological processes such as lactation in females and a developmental postâweaning fast in juveniles. Previous studies have shown that ÎŽ13C and ÎŽ15N values are affected by starvation, but the precise effects of fasting associated to lactation and postâweaning fast in seals remain poorly understood. Methods: To examine the effect of lactation and postâweaning fast on stable isotope ratios in GS and NES, blood and hair were sampled from twentyâone GS motherâpup pairs on the Isle of May and on twentyâtwo weaned NES pups at Año Nuevo State Reserve during their respective breeding seasons. Milk samples were also collected from GS mothers. Stable isotope measurements were performed with an isotope ratio mass spectrometer coupled to an NâC elemental analyser. Results: Changes in stable isotope ratios in blood components during fasting were similar and weak between GS and NES mothers especially in blood cells (GS: Î15N = 0.05â°, Î13C = 0.02â°; NES: Î15N = 0.1â°, Î13C = 0.1â°). GS showed a 15N discrimination factor between maternal and pup blood cells and milk, but not for 13C. The strongest relationship between the isotopic compositions of the mother and the pup was observed in the blood cells. Conclusion: Isotopic consequences of lactation, fasting, and growth seem limited in NES and GS, especially in mediumâterm integrator tissues of feeding activity such as blood cells. Stable isotope ratios in the blood of pups and mothers are correlated. We observed a subtle motherâtoâpup fractionation factor. Our results suggest that pup blood cells are mostly relevant for exploring the ecology of female seals.PostprintPeer reviewe
Topology by Design in Magnetic nano-Materials: Artificial Spin Ice
Artificial Spin Ices are two dimensional arrays of magnetic, interacting
nano-structures whose geometry can be chosen at will, and whose elementary
degrees of freedom can be characterized directly. They were introduced at first
to study frustration in a controllable setting, to mimic the behavior of spin
ice rare earth pyrochlores, but at more useful temperature and field ranges and
with direct characterization, and to provide practical implementation to
celebrated, exactly solvable models of statistical mechanics previously devised
to gain an understanding of degenerate ensembles with residual entropy. With
the evolution of nano--fabrication and of experimental protocols it is now
possible to characterize the material in real-time, real-space, and to realize
virtually any geometry, for direct control over the collective dynamics. This
has recently opened a path toward the deliberate design of novel, exotic
states, not found in natural materials, and often characterized by topological
properties. Without any pretense of exhaustiveness, we will provide an
introduction to the material, the early works, and then, by reporting on more
recent results, we will proceed to describe the new direction, which includes
the design of desired topological states and their implications to kinetics.Comment: 29 pages, 13 figures, 116 references, Book Chapte
Parallel Evolution of Auditory Genes for Echolocation in Bats and Toothed Whales
The ability of bats and toothed whales to echolocate is a remarkable case of convergent evolution. Previous genetic studies have documented parallel evolution of nucleotide sequences in Prestin and KCNQ4, both of which are associated with voltage motility during the cochlear amplification of signals. Echolocation involves complex mechanisms. The most important factors include cochlear amplification, nerve transmission, and signal re-coding. Herein, we screen three genes that play different roles in this auditory system. Cadherin 23 (Cdh23) and its ligand, protocadherin 15 (Pcdh15), are essential for bundling motility in the sensory hair. Otoferlin (Otof) responds to nerve signal transmission in the auditory inner hair cell. Signals of parallel evolution occur in all three genes in the three groups of echolocatorsâtwo groups of bats (Yangochiroptera and Rhinolophoidea) plus the dolphin. Significant signals of positive selection also occur in Cdh23 in the Rhinolophoidea and dolphin, and Pcdh15 in Yangochiroptera. In addition, adult echolocating bats have higher levels of Otof expression in the auditory cortex than do their embryos and non-echolocation bats. Cdh23 and Pcdh15 encode the upper and lower parts of tip-links, and both genes show signals of convergent evolution and positive selection in echolocators, implying that they may co-evolve to optimize cochlear amplification. Convergent evolution and expression patterns of Otof suggest the potential role of nerve and brain in echolocation. Our synthesis of gene sequence and gene expression analyses reveals that positive selection, parallel evolution, and perhaps co-evolution and gene expression affect multiple hearing genes that play different roles in audition, including voltage and bundle motility in cochlear amplification, nerve transmission, and brain function
Sex bias in biopsy samples collected from free-ranging dolphins
Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in European Journal of Wildlife Research 56 (2010): 151-158, doi:10.1007/s10344-009-0299-7.Biological samples of free-ranging dolphins are increasingly used to gain information on
population structure and ecology. In small cetaceans, the gender of individuals usually cannot
be determined at sea, and population sex ratio has to be inferred indirectly. We used
molecular sexing to determine the gender of 340 biopsy samples of bottlenose dolphins,
Tursiops truncatus, spotted dolphins, Stenella frontalis, and common dolphins, Delphinus
delphis, collected around the Azores and Madeira. Sex ratio was globally skewed in favor of
males, and differed between species and archipelagos. Skew was probably influenced by the
selectivity of biopsy collectors and seasonal or year-round predominance of males in natural
populations. Skew was also influenced by sampling duration and intensity. In the Azores,
when several samples were successively collected within the same group, the proportion of
female samples decreased as a function of sample order. This trend indicated a tendency for
females to increasingly avoid the boat while samples were being collected. It showed that
males and females reacted differently to the perturbation caused by the biopsy sampling
process (i.e. sample collection and driving style).Portuguese Foundation for
Science and Technology (FCT) and the FEDER program for funding the CETAMARH
(POCTI/BSE/38991/01) and the GOLFINICHO (POCI/BIA-BDE/61009/2004) projects,
S.Q.'s post-doctoral grants (IMAR/FCT- PDOC-006/2001-MoleGen and
SFRH/BPD/19680/2004), M.A.S.'s doctoral (SFRH/BD/8609/2002) and post-doctoral
(SFRH/BPD/29841/2006) grants, S.M.'s investigation assistant grant
(CETAMARHII/POCTI/BSE/38991/2001) and I.C.'s investigation assistant grants
(IMAR/FCT/GOLFINICHO/001/2005 and IMAR/FCT/GOLFINICHO/004/2006). FCT for its pluri-annual funding to Research Unit #531 and the EU funded
program Interreg IIIb for funding the MACETUS project (MAC/4.2/M10) as well as R.P. and S.M.âs grants (IMAR/INTERREGIIIb/MACETUS/MAC1/2)
A New Dolphin Species, the Burrunan Dolphin Tursiops australis sp. nov., Endemic to Southern Australian Coastal Waters
Small coastal dolphins endemic to south-eastern Australia have variously been assigned to described species Tursiops truncatus, T. aduncus or T. maugeanus; however the specific affinities of these animals is controversial and have recently been questioned. Historically âthe southern Australian Tursiopsâ was identified as unique and was formally named Tursiops maugeanus but was later synonymised with T. truncatus. Morphologically, these coastal dolphins share some characters with both aforementioned recognised Tursiops species, but they also possess unique characters not found in either. Recent mtDNA and microsatellite genetic evidence indicates deep evolutionary divergence between this dolphin and the two currently recognised Tursiops species. However, in accordance with the recommendations of the Workshop on Cetacean Systematics, and the Unified Species Concept the use of molecular evidence alone is inadequate for describing new species. Here we describe the macro-morphological, colouration and cranial characters of these animals, assess the available and new genetic data, and conclude that multiple lines of evidence clearly indicate a new species of dolphin. We demonstrate that the syntype material of T. maugeanus comprises two different species, one of which is the historical âsouthern form of Tursiopsâ most similar to T. truncatus, and the other is representative of the new species and requires formal classification. These dolphins are here described as Tursiops australis sp. nov., with the common name of âBurrunan Dolphinâ following Australian aboriginal narrative. The recognition of T. australis sp. nov. is particularly significant given the endemism of this new species to a small geographic region of southern and south-eastern Australia, where only two small resident populations in close proximity to a major urban and agricultural centre are known, giving them a high conservation value and making them susceptible to numerous anthropogenic threats
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